Subject: [homenet] DHCPv4 Subnet Allocation, and IPv4 Router Advertisements

From: Alexandru Petrescu <[email-masked]>
Date: Wed, 22 Jul 2015 13:44:52 +0200

Hi,

With respect to implementation report.

Do you need DHCPv4 Subnet Allocation and/or IPv4 Router Advertisements 
(RFC6656 and RFC1256)?

Alex

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From: David Lamparter <[email-masked]>
Date: Wed, 22 Jul 2015 13:52:32 +0200

> Do you need DHCPv4 Subnet Allocation and/or IPv4 Router Advertisements 

hncp-07 section 7.4 says:
[...] The winner is the router (connected to the Common Link)
advertising the greatest L-capability. [...] The elected router MUST
provide DHCPv4 services on the given link.

hncp-07 section 10 says on the election:
[...] between 1 and 7 included (4 is the default) if the router is
capable of running a legacy DHCPv4 server offering IPv4 addresses to
clients and 0 otherwise. [...]

So, L=0 implies the router can't do a DHCPv4 server.  And if you have a
link where all routers have L=0, there will not be DHCPv4 on that link.
(Which is, I guess, how you would do sunset4?)

Not sure if any of this is changing in -08;  I do agree with Alexandru
in that there is a need for a mechanism to ditch IPv4 for individual
v6-only devices or complete v6-only homenets.

NB: Prefix assignment is a different question.

-David

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From: Alexandru Petrescu <[email-masked]>
Date: Wed, 22 Jul 2015 14:21:34 +0200

> provide DHCPv4 services on the given link.

Sounds as if you actually want a "The elected router MAY provide DHCPv4 
service on the given link, and only until year 2020".?

Or maybe you want to have an RFC today to be able to update it in a few 
years time? (remove the MUST).

> (Which is, I guess, how you would do sunset4?)

You seem to be saying that '0' is somehow a priviledged value.  Maybe 
make _that_ a 'default' (not '4') and make _that_ a MUST?
> v6-only devices or complete v6-only homenets.

YEs, trying to set my mind about this being IPv6-only in a brief time, 
and IPv4 still there, but not in the way.

IPv6 is default, the doc should read mainly IPv6, IPv4 in the appendix, 
or as exceptional additional documents for those who really need it.

Just some comments...

> NB: Prefix assignment is a different question.

I agree.

Alex

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From: Juliusz Chroboczek <[email-masked]>
Date: Wed, 22 Jul 2015 18:17:01 +0200

> years time? (remove the MUST).

Not quite.

Prefix assignment is optional -- for every prefix P delegated to the
Homenet and for every link L, it is a local policy decision whether you
assign a prefix Q carved out of P to link L.  In particular, it is
perfectly legal to ignore all IPv4 delegated prefixes.

In HNCP-06, which is what I implemented, you MUST implement a DHCPv4
server if you do IPv4 prefix assignment, but you're allowed to do neither
v4 prefix assignment nor DHCPv4 service.

(In the latest version, there's a loophole that allows you to work around
this particular MUST.)

Altogether, the requirements make sense to me.

-- Juliusz